1. Field of the Invention
This invention relates to a method of manufacturing a multilayer molded article for electrical applications comprising an inner semiconductive layer, an electrically insulating layer, and an outer semiconductive layer. In one aspect, the process includes first crosslinking the semiconductive layers individually, and then injecting an insulation resin between the crosslinked semiconductive layers. In one aspect, the invention relates to a process in which the insulation layer is crosslinked using an organopolysiloxane containing two or more functional end groups so as to adhere it to one or more of the crosslinked semiconductive layers.
2. Description of the Related Art
For high temperature resistance, multilayered molded articles, which are generally made from elastomeric materials, are crosslinked. The dominant materials currently used in the industry include peroxide crosslinkable compounds based on ethylene-propylene-diene monomer (EPDM) or silicone rubbers. The multilayered molded articles are manufactured via multiple-step injection molding using in-mold vulcanization at high temperature. Additional post-molding cure in a high temperature autoclave is also used. Co-extrusion of the tubular portion of these parts is also practiced in the industry. The semiconductive and insulation layers are bonded together during a high temperature manufacturing step. Layer bonding is achieved via interfacial crosslinking using the peroxide present in the adjoining layers. Layer bonding is very important to prevent inter-layer dislocation during installation or loss of insulation performance (e.g. air voids or gaps) at the interface which is a region of high electrical stress which can lead to part failure.